Upper Lake Garda area sewerage system (Italy)

THE PROJECT OF THE NEW COLLECTOR SERVING THE VERONESE (EASTERN) SHORE OF THE NORTHERN PART OF LAKE GARDA, AIMS AT IMPROVING THE SERVICE OF COLLECTION, TRANSFER AND TREATMENT OF THE SEWAGE EFFLUENTS FROM THE MUNICIPALITIES OF MALCESINE, BRENZONE AND TORRI DEL BENACO AND INDIRECTLY IMPROVING AND PRESERVING THE ENVIRONMENT OF LAKE GARDA.

Project: Improvement of the sewerage system in the upper part of Lake Garda

Location: Province of Verona, Italy

Client: Azienda Gardesana Servizi S.p.A.

Cost of total Works: € 32,846,700

Services: Preliminary Design

Period: 2011

The existing Garda collector is a hydraulic structure built in the 1970’s to collect the wastewater (almost entirely civil waste) from the municipalities located along the shore of the Lake Garda and some of the nearby towns.

It is a complex project due to the difficult morphology of the territory, which leaves little space available between the steep slopes of the Mount Baldo, and the lake basin, adjacent to the Gardesana road, which, in many parts, occupies the only available space between the mountains and the lake.

The present collector shows a number of infiltration problems of “parasitic” waters coming from the lake and from local water-bearing strata, which manage to penetrate the current piping system to the detriment of its performance.

The collector required the employment of numerous pumping systems due to its considerable length (approximately 30 km, between Navene di Malcesine and Brancolino di Torri del Benaco) and to the fact that the local residents are all located at more or less the same altitude as the lake (approximately 64.50 m.a.s.l.).The new project foresees the use of ductile cast iron, instead of the current concrete structures. The new piping system has a perfect air-tight sealing and therefore does not allow the penetration of water from the outside.

This also enables the achievement of an important environmental goal because it avoids the mixing of wastewater with clean waters from the lake or water-bearing strata. Furthermore, the joints in the ductile cast iron system (each 6 m long) have air-tight sealing, while the joints in the concrete piping system (just 2,5 m long and therefore considerably more numerous) are significantly weaker.

In order to avoid the introduction in the new collector of significant amounts of rainwater, which in urban settlements becomes mixed with the only mixed network available, the project foresees the provision of the secondary inlets with a number of spillways. There will also be a spillway directing waters to the closest rainwater tank, where the amount of water diverted will be filtered through a screening system, grit removal and flow equalization structure, before being released in the lake.

The project also intends to use the current collector (or part of it) for rainwater. It was planned to rehabilitate all the piping with a settlement level of 120 cm on the hydrometer of Peschiera. These pipes will form a system of independent branches all directed towards rainwater treatment tanks.

The construction of the new collector, as well as significantly reducing eddy waters that create problems in the wastewater treatment plant of Peschiera and also for the pumping station along the lake, protect the environment since with the lower flow rates the emergency spillways should no longer be activated.